1. Field of the Invention
This invention relates to a production of aliphatic and cycloaliphatic diamines. More especially, this invention relates to a two-step process for the production of aliphatic and cycloaliphatic diamines by reaction of dialdehydes with a monoamine to form the corresponding diazomethyne and subsequent reaction of the so-formed diazomethyne with ammonia and hydrogen in the presence of a hydrogenation catalyst (aminating hydrogenation).
2. Discussion of the Prior Art
Diamines, especially .alpha.,.omega.-alkylene diamines, for example, hexamethylene diamine and also cycloaliphatic diamines such as 1,4-diaminocyclohexane are valuable intermediate products for a great number of chemical syntheses. They find use in the production of polyamides or of polyurethanes as well as curing agent component for epoxide resins.
Aliphatic or cycloaliphatic diamines may be produced by hydrogenation of the corresponding dinitriles. However, since the production of the dinitriles is commercially expensive, this method permits the economic preparation of diamines only in exceptional cases.
Another mode of operation for the production of diamines starts from dialcohols which are reacted with ammonia. Since the reaction requires high temperatures which favor the formation of by-products, the yield is only low.
Instead of reacting dialcohols with ammonia, it is further known to react dialdehydes in the presence of catalysts with ammonia and hydrogen in one step. However, the achievable yields are unsatisfactory also in this process because the aldehydes enter into addition and condensation reactions and polyimines are formed.
Therefore, due to the great importance of the diamines, there was the problem to develop a process which permits the production of this class of compounds in a high yield and with a technically justifiable expense.